Are "Drugged Waters" a Water Quality Threat?
Developed to promote human health and well being, certain pharmaceuticals are now attracting attention as a potentially new class of water pollutants. Such drugs as antibiotics, antidepressants, birth control pills, seizure medication, cancer treatments, pain killers, tranquilizers and cholesterol-lowering compounds have been detected in varied water sources.
Where do they come from? Pharmaceutical industries, hospitals and other medical facilities are obvious sources, but households also contribute a significant share. People often dispose of unused medicines by flushing them down toilets, and human excreta can contain varied incompletely metabolized medicines. These drugs can pass intact through conventional sewage treatment facilities, into waterways, lakes and even aquifers. Further, discarded pharmaceuticals often end up at dumps and land fills, posing a threat to underlying groundwater.
Farm animals also are a source of pharmaceuticals entering the environment, through their ingestion of hormones, antibiotics and veterinary medicines. (About 40 percent of U.S.-produced antibiotics are fed to livestock as growth enhancers.) Manure containing traces of such pharmaceuticals is spread on land and can then wash off into surface water and even percolate into groundwater.
Along with pharmaceuticals, personal care products also are showing up in water. Generally these chemicals are the active ingredients or preservatives in cosmetics, toiletries or fragrances. For example, nitro musks, used as a fragrance in many cosmetics, detergents, toiletries and other personal care products, have attracted concern because of their persistence and possible adverse environmental impacts. Some countries have taken action to ban nitro musks. Also, sun screen agents have been detected in lakes and fish.
Researchers Christian G. Daughton and Thomas A. Ternes reported in the December issue of "Environmental Health Perspectives" that the amount of pharmaceuticals and personal care products entering the environment annually is about equal to the amount of pesticides used each year.
Concern about the water quality impacts of these chemicals first gained prominence in Europe, where for over a decade scientists have been checking lakes, streams, and groundwater for pharmaceutical contamination. American officials and scientists are taking note, with two recent US professional organizations - the National Ground Water Associations and the American Chemical Society - addressing the issue at their annual meetings this summer.
The issue emerged in Europe about ten years ago, when German environmental scientists found clofibric acid, a cholesterol-lowering drug, in groundwater beneath a German water treatment plant. They later found clofibric acid throughout local waters, and a further search found phenazone and fenofibrate, drugs used to regulate concentrations of lipids in the blood, and analgesics such as ibuprofen and diclofenac in groundwater under a sewage plant. Meanwhile other European researchers discovered chemotherapy drugs, antibiotics and hormones in drinking water sources.
In the United States, the issue might have attracted earlier notice if officials had followed up on observations made 20 years ago. At that time, EPA scientists found that sludge from a US sewage-treatment plant contained excreted aspirin, caffeine and nicotine. At the time, no significance was attached to the findings.
In Phoenix about this time another event occurred that also might have alerted officials that pharmaceuticals could pose a water quality threat. Herman Bouwer of the US Agricultural Research Service in Phoenix recalls that clofibric acid was found in groundwater below infiltration basins that were artificially recharging groundwater with sewage effluent. Bouwer says more attention should have been paid to the finding; if clofibric acid could pass through a sewage treatment plant and percolate into the groundwater so also could many other drugs.
Europeans, however, took the lead in researching the issue. In the mid 1990s, Thomas A. Ternes, a chemist in Wiesbaden, Germany, investigated what happens to prescribed medicines after they are excreted. Ternes knew that many such drugs are prescribed, and that little was known of the environmental effects of these compounds after they are excreted. He researched the presence of drugs in sewage, treated water and rivers, and his findings surprised him.
Expecting to identify a few medicinal compounds he instead found 30 of the 60 common pharmaceuticals that he surveyed. Drugs he identified included lipid-lowering drugs, antibiotics, analgesics, antiseptics, beta-blocker heart drugs, residues of drugs for controlling epilepsy as well as drugs serving as contrast agents for diagnostic X rays.
Results of recent research in North America also indicate reason for concern. At the June National Groundwater Association conference, Glen R. Boyd, a Tulane University civil engineer, reported detecting drugs in the Mississippi River, Lake Ponchetrain and in Tulane's tap water. Boyd and his team found in tested waters low levels of clofibric acid, the pain killer naproxen and the hormone estrone. Samples of Tulane's tap water showed estrone averaging 45 parts per trillion with a high of 80 parts per trillion.
At the recent American Chemical Society conference, Chris Metcalfe of Trent University in Ontario reported finding a vast array of drugs leaving Canadian sewage treatment plants, at times at higher levels than what is reported in Germany. Such drugs included anticancer agents, psychiatric drugs and anti-inflammatory compounds. North American treatment plants may show higher levels of pharmaceuticals because they often lack the technological sophistication of German facilities.
The U.S.G.S. is currently conducting the first nationwide assessment of "emerging contaminants" found in selected streams, including the occurrence of human and veterinary pharmaceuticals, sex and steroidal hormones and other drugs such as antidepressants and antacids. One hundred stream sites were identified, representing a wide variety of geographical and hydrogeological settings. Four of these sites are in Arizona: Santa Cruz River at Cortaro Road; Santa Cruz River near Rio Rico; Salt River below 91st Ave. sewage treatment plant; and Gila River above diversions at Gillespie Dam.
Stream sites were chosen that were expected to be highly susceptible to contamination by targeted compounds. Testing the sites will provide an initial indication of the potential for these compounds to enter the environment, as well provide an opportunity for developing suitable laboratory methods for measuring compounds in environmental samples at very low (sub-ppb) levels.
Detected contaminants include caffeine, which was the highest-volume pollutant, codeine, cholesterol-lowering agents, antidepressants, and Premarin, an estrogen replacement drug taken by about 9 million women. Also chemotherapy agents were found downstream from hospitals treating cancer patients. Final results from the study are expected to be released in the fall. For additional information about the U.S.G.S. study check the website: toxics.usgs.gov/regional/emc.html
What risk does chronic exposure to trace concentrations of pharmaceuticals pose to humans or wildlife? Some scientists believe pharmaceuticals do not pose problems to humans since they occur at low concentrations in water. Other scientists say long-term and synergistic effects of pharmaceuticals and similar chemicals on humans are not known and advise caution. They are concerned that many of these drugs have the potential of interfering with hormone production. Chemicals with this effect are called endocrine disrupters and are attracting the attention of water quality experts.
To some scientists the release of antibiotics into waterways is particularly worrisome. They fear the release may result in disease-causing bacteria to become immune to treatment and that drug-resistant diseases will develop.
Scientists generally agree that aquatic life is most at risk, its life cycle, from birth to death, occurring within potentially drug-contaminated waters. For example, antidepressants have been blamed for altering sperm levels and spawning patterns in marine life. Most studies of pharmaceutical and pharmaceutically active chemicals in water have mostly focused on aquatic animals.
For example, recent British research suggest that estrogen, the female sex hormone, is primarily responsible for deforming reproductive systems of fish, noting that blood plasma from male trout living below sewage treatment plants had the female egg protein vitellogenin. This finding would seem to be consistent with what US researchers suspect has occurred downstream from treatment plants in Las Vegas and Minneapolis. Carp in these areas show the same effects as the British fish.
Some scientists believe arid regions of the West are especially vulnerable to the effects of drug-contaminated effluent. These areas are more likely to have streams that rely almost entirely on effluent for flow, especially during dry months. Further, effluent is extensively used in irrigation and even for recharging drinking water aquifers. Also, areas of the West have attracted large number of retired people who are likely to use more pharmaceuticals than other population segments; thus more pharmaceuticals in wastewater.
Mapping of Human Genome
Means More Drugs, Possibly More Pollution
Pharmaceuticals are greatly increasing in numbers and kinds, with greater likelihood of releases into the environment. Before the recent announcement of the almost complete categorization of the human genome, Christian G. Daughton and Thomas A. Ternes wrote in an article that appeared in Environmental Health Perspectives, "The enormous array of pharmaceuticals will continue to diversify and grow as the human genome is mapped. Today there are about 500 distinct biochemical receptors at which drugs are targeted. ... The number of targets is expected to increase 20-fold (yielding 3,000 to 10,000 drug targets) in the near future." The authors warn, "This explosion in new drugs will severely exacerbate our limited knowledge of drugs in the environment and possibly increase the exposure/effects risks to nontarget organisms."